1. Setting of the Invention
In the practice of secondary recovery of petroleum from subterranean formations, waterflooding is commonly employed. In such operations water is injected down an input well and into the formation to displace oil from the formation towards a producing well through which the oil is recovered. Additives such as sodium carbonate or sodium hydroxide in waterfloods have been used to improve oil recovery. Additionally, surfactants have also been utilized to improve oil recovery. However, both techniques, although effective, are expensive and are applicable only to limited types of formations bearing special varieties of petroleum.
2. Pertinent Art
Pertinent art in the area is illustrated by U.S. Pat. No. 3,757,861 issued to Willis G. Routson on Sept. 11, 1973 and entitled "Oil Recovery Employing Peroxides and Alkalis". The process employed by Routson requires injection of an aqueous solution containing at least about 5% by weight of an inorganic peroxide in an amount of at least about 0.04 pore volume of the formation followed by or injected with an aqueous solution containing at least about 0.05% by weight of alkaline agent in an amount at least equal to that of the peroxide solution. This peroxide/alkaline agent pad was in turn forced through the formation by solutions of water containing mobility control agents such as xanthan gum. Peroxides and and alkalines in Routson are allowed to co-act and the products of reaction of the peroxide and the copolymer are maintained in the bank which is then displaced into the formation toward one or more producing walls.
Additional pertinent art is illustrated by U.S. Pat. Nos. 3,298,436, 3,330,347 and 3,344,858 which discloses production of surfactant compounds in situ in an oil bearing formation by the injection of an acid compound followed by a caustic solution. Such operations, however, are, as mentioned above, inherently expensive.